1. Field of the Invention
This invention relates to a disc cartridge having accommodated therein a disc used as a recording medium for information signals, such as an optical disc or a magneto-optical disc. More particularly, it related to a disc cartridge comprised of a cartridge main body having accommodated therein a disc and provided with an aperture for laying a part of the disc to outside across its inner and outer peripheries and a shutter member movably mounted thereon for opening and closing said aperture.
2. Description of the Related Art
As a recording medium for information signals, a disc such as a magnetic disc, an optical disc or a magneto-optical disc, has been proposed. This disc has a disk-shaped substrate having its one major surface coated with a signal recording layer. The inner periphery of the disc, provided with a centering hole, is designed as a chucking region to be chucked by a disc rotating unit of a disc recording and/or reproducing apparatus. A region of the disc extending from the outer edge of the chucking region to the outer periphery is designed as a signal recording region.
For preventing deposition of dust and dirt or pollution by contact with hands or fingers, and for achieving handling ease, the disc is housed in a square-shaped casing-like cartridge main body so as to be constructed as a disc cartridge.
With such a disc cartridge, the disc housed within the cartridge main body is rotatable within the cartridge main body. A chucking aperture for exposing the chucking portion of the disc to the outside is provided in one of the major surfaces of the disc cartridge. A recording/reproducing aperture for laying at least a part of the major surface of the disc to the outside across its inner and outer peripheries is also provided in one of the major surfaces of the disc cartridge. Information signals may be written on or reproduced from the signal recording layer of the disc accommodated in the cartridge main body via the recording/reproducing aperture whilst the disc has its chucking portion chucked by the disc rotating unit via the chucking aperture on loading the disc cartridge in position within the disc recording and/or reproducing apparatus.
With the disc cartridge, for preventing intrusion of dust and dirt into the cartridge main body for protecting the disc, the recording/reproducing aperture is closed by the shutter member when the disc cartridge is out of use. The shutter member has a plate portion of a size to close the recording/reproducing aperture. The shutter member may be moved along a lateral side of the cartridge main body by having a proximal part of the plate portion supported by the lateral side of the cartridge main body. The shutter member is adapted for closing the recording/reproducing aperture with the plate portion.
With such a disc cartridge, the shutter member may be formed by bending a metallic plate, or by molding from a synthetic resin.
However, if it is attempted to produce the shutter member of the same shape as the shutter member formed by bending the metallic plate by molding of a synthetic resin, not only is molding rendered difficult, but the shutter member having sufficient mechanical strength cannot be produced. On the other hand, if the disc cartridge is constructed with the shutter member having a shape suitable for integral molding from the synthetic resin, the disc cartridge cannot be employed in a disc recording and/or reproducing apparatus intended to be used with the disc cartridge having the shutter member formed of the metallic plate. In other words, the opening/closing operation of the shutter member produced in conformity to respective properties of the different materials cannot be performed smoothly in a shutter mechanism of the disc recording and/or reproducing apparatus.
On the other hand, the shutter member having a suitable shape to be molded from the synthetic resin can be produced only with extremely difficultly by bending the metallic plate.